Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Gravity Drive and Free-Fall

  1. Aug 19, 2013 #1
    I have a completely speculative sci-fi question I've been wrestling with, and I'd love some feedback from better minds than my own:

    Lets assume we develop the technology to artificially generate gravity without mass (maybe using electrogravitics). We build a spaceship that can project a gravity well at a fixed distance in front of it. This in turn pulls the ship towards the gravity well, while simultaneously moving the gravity well itself (kind of like dangling a carrot in front of a horse).

    1.) Would people aboard the spaceship essentially experience free-fall (weightlessness), as they'd be constantly falling towards the gravity well but so is the ship (like being on a reduced-gravity aircraft)?

    On a related note:

    2.) What are the effects on a human body of falling into a gravity well that is greater than 1 g, when atmosphere is removed from the equation?

    Let's say you're a human in a space suit and you're falling down towards a very dense rock (where the gravity is 3 g) that has no atmosphere. When you're falling, you're essentially in free-fall, so it's like your weightless. Would you have trouble with blood flow and and other issues normally associated with high g-force on the human body (such as when accelerating in a fighter jet)?
     
  2. jcsd
  3. Aug 20, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Probably, but it could depend on the fictional device (how does it accelerate the spot of attraction, by the way?). If it is close to the spacecraft, different parts of the spacecraft could experience a different acceleration.

    In a uniform field: nothing, you cannot notice it at all (unless you look at other objects as reference). In a non-uniform field, you can feel the non-uniformity (at least in theory).
     
  4. Sep 22, 2013 #3
    The reason that you're affected by high gees is that there's something stopping you from falling freely in it (e.g. the ground or your seat). If there's nothing between you and the gravitational source, you won't feel anything until tidal forces come into the equation. Basically, your feet are closer to the source than your head, so they're pulled harder, and if the difference becomes great enough, you're torn apart. Things like stars and planets aren't dense enough to create noticeable tidal forces on a human scale at any distance, but neutron stars and black holes fit the bill at close distances.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook